1. Field of the Invention
The present invention relates to a laser machining robot having a laser machining head, mounted on a tip end of a robot arm, which conducts the laser machining and carrying out the laser machining while moving a laser machining head. More specifically, the present invention relates to a technique for moving a laser machining robot while keeping a constant distance between a tip end of a laser machining head and a workpiece during laser machining.
2. Description of the Related Art
In recent years, needs of three-dimensional machining by a laser machining apparatus using a robot in fields of general industries including the automobile industry increase. Generally, it is required that a laser machining head has high positional accuracy so as to keep optimum a distance between the laser machining head and a workpiece optimum in laser machining. In addition, some workpieces have fluctuations in shape, size, and position. In order to deal with such fluctuations, a method of controlling a position of the laser machining head at real time during machining is adopted.
However, even if this method is adopted, the following disadvantages often occur. In three-dimensional machining, a vibration is generated following a rapid acceleration or deceleration of the robot and a locus of a tip end point of the laser machining head cannot be accurately controlled. To avoid the disadvantages, a method of inputting an empirically obtained velocity condition at each time is proposed (see, for example, Japanese Patent Application Laid-Open No. 6-210475).
With this method, however, it is necessary to specify a condition in which a stable machining state can be realized while preventing an increase in machining time as much as possible by repeatedly setting a robot velocity near a section at which the vibration is generated and setting a laser output corresponding to a velocity thus set through trial and error. It disadvantageously takes lots of time to perform an operation for specifying the condition.